#include <stdio.h>
#include <stdlib.h>
typedef enum {
	pawn = 1,
	knight = 2,
	bishop = 3,
	rook = 4,
	queen = 5,
	king = 6,
} piece_t;
typedef struct Vector {
	int mx;
	int my;	
} vector_t;
vector_t init_vector(int mx, int my) {
	vector_t vector;
	vector.mx = mx;
	vector.my = my;
	return vector;
}
typedef struct VectorP {
	vector_t* vectors;
	int length;
} vectorp_t;
vectorp_t init_vectorp(vector_t* vectors, int length) {
	vectorp_t vectorP;
	vectorP.vectors = vectors;
	vectorP.length = length;
	return vectorP;
}
void draw_board(int board[8][8]) {
	printf("  ABCDEFGH\n");
	for(int r = 0; r < 8; r++) {
		char* line = calloc(10, sizeof(char));
		line[0] = '8' - r;
		line[1] = ' ';
		for(int c = 0; c < 8; c++) {		
			if(board[c][r] <= 6) {
				switch(board[c][r]) {
					case 0:
						line[c + 2] = ' ';
						break;
					case pawn:
						line[c + 2] = 'P';
						break;
					case knight:
						line[c + 2] = 'N';
						break;
					case bishop:
						line[c + 2] = 'B';
						break;
					case rook:
						line[c + 2] = 'R';
						break;
					case queen:
						line[c + 2] = 'Q';
						break;
					case king:
						line[c + 2] = 'K';
						break;
				}
			}
			else {
				switch(board[c][r] - 6) {
					case 0:
						line[c + 2] = ' ';
						break;
					case pawn:
						line[c + 2] = 'p';
						break;
					case knight:
						line[c + 2] = 'n';
						break;
					case bishop:
						line[c + 2] = 'b';
						break;
					case rook:
						line[c + 2] = 'r';
						break;
					case queen:
						line[c + 2] = 'q';
						break;
					case king:
						line[c + 2] = 'k';
						break;
				}
			}
		}
		printf(line);
		printf("\n");
		free(line);
	}
}
int in_board(vector_t position) {
	return position.mx < 8 && position.mx >= 0 && position.my < 8 && position.my >= 0;
}
int is_empty(int board[8][8], vector_t position) {
	return board[position.mx][position.my] == 0;
}
int get_owner(int board[8][8], vector_t position) {

}
int 
vectorp_t get_moves(int board[8][8], vector_t position, piece_t piece) {
	vector_t* moves = malloc(27 * sizeof(vector_t));
	int moveCount = 0;
	if(piece == pawn) {
		vector_t move1 = init_vector(position.mx, position.my - 1);
		if(in_board(move1) && is_empty(board, move1)) {
			moves[0] = move1;
			moveCount++;
			if(position.my == 6) {
				vector_t move2 = init_vector(position.mx, position.my - 2);
				if(is_empty(board, move2)) {
					moves[1] = move2;
					moveCount++;
				}
			}
		}
		vector_t captureL = init_vector(position.mx - 1, position.my - 1);
		if(in_board(captureL) && 
		return init_vectorp(moves, moveCount);
	}
	else if(piece == pawn + 6) {
		vector_t move1 = init_vector(position.mx, position.my + 1);
		if(in_board(move1) && is_empty(board, move1)) {
			moves[0] = move1;
			moveCount++;
			if(position.my == 1) {
				vector_t move2 = init_vector(position.mx, position.my + 2);
				if(is_empty(board, move2)) {
					moves[1] = move2;
					moveCount++;
				}
			}
		}
		return init_vectorp(moves, moveCount);
	}
}
vector_t user_input_pos() {
	char* inputString = malloc(3 * sizeof(char));
	vector_t pos;
	printf("Enter coordinates: ");
	scanf("%2s", inputString);
	for(int i = 0; i < 2; i++) {
		if(inputString[i] <= '9' && inputString[i] >= '0') {
			pos.my = 8 - (inputString[i] - '0');
		}
		else if(inputString[i] <= 'Z' && inputString[i] >= 'A') {
			pos.mx = inputString[i] - 'A';
		}
		else if(inputString[i] <= 'z' && inputString[i] >= 'a') {
			pos.mx = inputString[i] - 'a';
		}
		else {
			return init_vector(-1, -1);
		}
	}
	free(inputString);
	return pos;
}
//converts board coordinates into algebraic notation
char* get_readable_coords(vector_t position) {
	char* output = malloc(3 * sizeof(char));
	output[0] = 'A' + position.mx;
	output[1] = '8' - position.my;
	output[2] = '\0';
	return output;
}
void clear_screen() {
	system("@cls||clear");
}
void warn_user(char* message) {
	clear_screen();
	printf("\n");
	printf(message);
	printf("\nPress any key to continue...\n");
	while(getchar() != '\n');
	getchar();
}
int main() {
	int board[8][8] = { 
		{ rook + 6, pawn + 6, 0, 0, 0, 0, pawn, rook }, 
		{ knight + 6, pawn + 6, 0, 0, 0, 0, pawn, knight },
		{ bishop + 6, pawn + 6, 0, 0, 0, 0, pawn, bishop },
		{ queen + 6, pawn + 6, 0, 0, 0, 0, pawn, queen },
		{ king + 6, pawn + 6, 0, 0, 0, 0, pawn, king },
		{ bishop + 6, pawn + 6, 0, 0, 0, 0, pawn, bishop },
		{ knight + 6, pawn + 6, 0, 0, 0, 0, pawn, knight },
		{ rook + 6, pawn + 6, 0, 0, 0, 0, pawn, rook }
	}; 
	int turn = 0;
	while(1) {
		//draw the board, write some info
		clear_screen(board);
		draw_board(board);
		printf(turn == 0 ? "\nWhite's turn\n" : "\nBlack's turn\n");
		printf("Enter the coordinates of the piece you want to move\n");
		//get the selection for the piece to be moved
		vector_t selection = user_input_pos();
		int selectedPiece = board[selection.mx][selection.my];
		//check if the piece is of the right colour, and that there is a piece there
		if(selectedPiece == 0 || (selectedPiece > 6 && turn == 0) || (selectedPiece <= 6 && turn == 1)) {
			warn_user("Invalid selection!");
			continue;
		}
		printf("Selected piece: ");
		printf("%d", selectedPiece);
		printf("\n");
		vectorp_t moves = get_moves(board, selection, selectedPiece);
		if(moves.length == 0) {
			warn_user("That piece has no valid moves!");
			continue;
		}
		printf("Valid moves: ");
		//write all the valid moves
		for(int i = 0; i < moves.length; i++) {
			char* readable_coords = get_readable_coords(moves.vectors[i]);
			printf(readable_coords);
			free(readable_coords);
			printf("; ");
		}
		printf("\nEnter the coordinates you would like to move that piece to, or enter < to go back\n");
		//get the selection for the location to move the piece to
		vector_t target = user_input_pos();
		if(target.mx == -1) {
			continue;
		}
		//check if target is in list of valid moves
		int match = 0;
		for(int i = 0; i < moves.length; i++) {
			if(moves.vectors[i].mx == target.mx && moves.vectors[i].my == target.my) {
				match = 1;
				break;
			}
		}
		if(!match) {
			warn_user("Invalid move");
			continue;
		}
		board[selection.mx][selection.my] = 0;
		board[target.mx][target.my] = selectedPiece;
		printf("\n");
		turn = !turn;
	}	
	return 0;
}